Provisioning satellite coverage

ABSTRACT

In one implementation, satellite coverage provisioning for a service area may be performed by updating power consumption states for satellites in a constellation of satellites and determining whether each satellite of the constellation is required to be in the minimal power consumption mode based on its updated power consumption state. For satellites that are not required to be in the minimal power consumption mode, a power consumption score may be calculated and these satellites may be sorted according to their respective power consumption scores. Based on the sorted order, it may be determined whether at least some of these satellites can be put into a reduced power consumption mode based on their respective power consumption scores and coverage of the service area. Then it may be determined if each of the satellites that are in the reduced power consumption mode can be put into the minimal power consumption mode.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a divisional of U.S. patent application Ser.No. 15/462,371, which was filed on Mar. 17, 2017, the disclosure ofwhich is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to provisioning satellite coverage.

BACKGROUND

Satellites provide important services in peoples' daily lives, such ascommunication (e.g., satellite phones), navigation (e.g., GlobalPositioning System (GPS)), surveillance, weather forecasting/monitoring,to name just a few. In some cases, a satellite service may be providedby a constellation of multiple satellites that collectively cover adesired service area. For example, the ubiquitous GPS service isprovided by a constellation of satellites operated by the United Statesgovernment, which is committed to maintaining the availability of atleast 24 operational GPS satellites, 95% of the time. To achieve thisgoal, the government has been flying 31 operational GPS satellites forthe past few years, according to http://www.gps.gov.

Existing satellite scheduling may focus on connection-oriented services,addressing single satellite and single orbit solutions. In addressingthis scenario, the scheduling approach can assess one or more feasiblesets of requests and then schedule the requests, optimizing the jobsover satellites and times. The scheduling of satellite services can beon a first in first out (FIFO) or priority queue basis, whereconstraints applied typically include time constraints and on-boardresource constraints.

SUMMARY

In one implementation, satellite coverage provisioning for a servicearea may be performed by updating power consumption states forsatellites in a constellation of satellites and determining whether eachsatellite of the constellation is required to be in the minimal powerconsumption mode based on its updated power consumption state. Forsatellites that are not required to be in the minimal power consumptionmode, a power consumption score may be calculated, and these satellitesmay be sorted according to their respective power consumption scores.Based on the sorted order, it may be determined whether at least some ofthese satellites can be put into a reduced power consumption mode basedon the respective power consumption scores and coverage of the servicearea. Then it may be determined if each of the satellites that are inthe reduced power consumption mode can be put into the minimal powerconsumption mode.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram of a constellation of satellitesproviding coverage.

FIG. 2 is a schematic block diagram of a satellite coverage provisioningsystem.

FIG. 3 is a schematic diagram of hysteresis for cumulative powerconsumption.

FIG. 4 is a flow diagram of an exemplary satellite coverage provisioningprocess.

FIG. 5 is a flow diagram of an exemplary iteration of a loop forsatellite coverage provisioning.

FIG. 6 is a flow diagram of an exemplary process for preparing eachsatellite.

FIG. 7 is a flow diagram of an exemplary process for updating status ofeach satellite.

FIG. 8 is a flow diagram of an exemplary process for determining whethera satellite may be put into a “High Idle” power level.

FIG. 9 is a flow diagram of an exemplary process for determining whethera satellite may be put into a “Low Idle” power level.

FIG. 10 is a block diagram demonstrating an exemplary computingapparatus configured to execute satellite coverage provisioning.

DESCRIPTION OF EXAMPLE IMPLEMENTATIONS

The concepts disclosed herein are illustrated through certainimplementations and aspects thereof, which are described in detailherein with reference to the accompanying drawings, wherein likereference numerals may refer to like features throughout. It is to beunderstood, however, that the disclosed concepts are not necessarilylimited to the illustrative implementations described below and thefollowing descriptions should be read in such light.

Additionally, the word exemplary may be used herein to refer to anexample, instance or illustration. As such, any reference to somethingas exemplary is not necessarily to be construed as preferred oradvantageous over something else.

Additionally, mathematical expressions are contained herein, and thoseprinciples conveyed thereby are to be taken as being thoroughlydescribed therewith. It is to be understood that where mathematics areused, such is for succinct description of the underlying principlesbeing explained and, unless otherwise expressed, no other purpose isimplied or should be inferred.

The figures described herein include schematic block diagramsillustrating various interoperating functional modules. Such diagramsare not necessarily intended to serve as electrical schematics. As such,interconnections illustrated may depict signal flow, variousinteroperations between functional components and/or processes, notnecessarily direct electrical connections between such components.Moreover, the functionality illustrated and described via separatecomponents need not be distributed as shown, and discrete blocks in thediagrams may not necessarily depict discrete electrical components.

Techniques described herein are directed to the provisioning ofsatellite coverage, for example, under constraints. In someimplementations, the provisioning of satellite coverage may includeselecting a subset of less than all satellites (or payloads on boardsuch satellites) from a constellation of satellites to provide servicecoverage related to information that is not known a priori (e.g.,receiving air traffic control surveillance data from aircraft) and/orwhen the service is not a connection-oriented service. For example,satellite coverage may be provisioned, not necessarily based on adefined set of tasks or connections, but rather to provide a capabilityand/or coverage to designated service areas, with onboard and systemconstraints considered. In one particular example, a constellation ofsatellites includes satellites configured to receive automatic dependentsurveillance-broadcast (ADS-B) signals from aircraft flying over theEarth. In some implementations, ADS-B receivers may be implementedwithin or be part of the primary payload of such satellites.Alternatively, ADS-B receivers may be implemented as so-called secondarypayloads hosted on such satellites. In either case, provisioning theADS-B service coverage provided by the constellation of satellites mayinclude selecting a subset of less than all satellites to provide thedesired service coverage during different time periods. This may beparticularly useful in implementations where the ADS-B receivers areimplemented as hosted payloads subject to certain constraints (e.g.,power consumption limits) imposed by the satellites busses, primarypayloads, etc. Upon review of this disclosure and appreciation of theconcepts disclosed herein, the ordinarily skilled artisan will recognizeother service provisioning contexts in which disclosed concepts can beapplied. The scope of the present disclosure is intended to encompassall such implementations.

FIG. 1 illustrates a plurality of satellites 102 providing coverage to aservice area 104 on Earth. The satellites 102(1), 102(2) and 102(3) maybe part of a constellation of satellites, which may comprise tens,hundreds or thousands of satellites depending, for example, on whatservice(s) are being provided by the constellation and/or the design ofthe constellation. It should be noted that although the singular wordservice occasionally may be used in the description herein, in somecases, multiple services may be provided by satellites according to thepresent disclosure, and, thus, the word service may represent a singleservice or a plurality of services. In some implementations, anindividual satellite 102 may have a single or primary payload configuredto provide one or multiple services. For example, an individualsatellite may have a primary payload configured to provide a space-basedsurveillance service. More particularly, an individual satellite mayhave a primary payload configured to provide a space-based ADS-Bservice, for example, by receiving ADS-B signals from aircraft equippedwith ADS-B avionics transmitting ADS-B messages. In suchimplementations, the payload may be or include an ADS-B receiver.Alternatively, an individual satellite may have a primary payloadconfigured to provide voice and/or data communication services toterrestrial subscribers. Additionally or alternatively, an individualsatellite 102 may have multiple payloads, each of which is configured toprovide one or more different services. For example, an individualsatellite may have a primary payload configured to provide voice and/ordata communication services to terrestrial subscribers and a secondaryor hosted payload configured to provide a space-based surveillanceservice such as, but not limited to, a space-based ADS-B surveillanceservice for aircraft equipped with ADS-B avionics transmitting ADS-Bsignals. In such implementations, the secondary or hosted payload may beor include an ADS-B receiver.

In some implementations, the satellites 102 may be part of aconstellation of low Earth orbit (LEO) satellites (that may or may notbe cross-linked to enable space-based communication between individualsatellites within the constellation). In such implementations, thesatellites 102 may orbit the Earth at altitudes, for example, between 99miles and 1,200 miles above the Earth's surface and with orbitalperiods, for example, between 88 minutes and 127 minutes. The footprintcovered by an individual satellite 102 (or payload on board thesatellite) may change as the satellite 102 orbits.

In one particular example, the satellites 102 may be arranged into anumber of orbital planes (e.g., 6 orbital planes) with an equal (ordifferent) number of satellites in each orbital plane (e.g., 11satellites per orbital plane) and, furthermore, the satellites 102 maybe configured such that collectively the satellites (or payloads onboard the satellites) are capable of providing coverage for the entireEarth or nearly the entire Earth. In this and other examples, thesatellites 102 may have polar or substantially polar orbits. As thesatellites orbit, the footprints that the satellites 102 (or payloads onboard the satellites) cover may change. Nevertheless, the collectivecoverage area that the satellites 102 (or payloads on board thesatellites) can provide may remain the same or substantially the sameover time (e.g., due to the coordinated arrangement and orbits of all ofthe satellites). Furthermore, in this example, individual satellites 102may include a primary payload configured to provide voice and/or datacommunication services to terrestrial subscribers and a secondary orhosted payload configured to provide a space-based ADS-B surveillanceservice. As such, satellites 102 collectively may be capable ofproviding both a global (or nearly global) voice and/or datacommunications service and a global (or nearly global) space-based ADS-Bsurveillance service. In such implementations, the provisioning of thevoice and/or data communications service may involve selecting a subsetof the primary payloads to provide the communications service atdifferent periods of time. Additionally or alternatively, theprovisioning of the space-based ADS-B surveillance service may involveselecting a subset of the secondary payloads to provide the space-basedADS-B surveillance service at different periods of time.

The service area 104 may be an area on the Earth's surface and, in somecases, the space above such area on the Earth's surface (e.g., in thecase of a space-based ADS-B surveillance service for aircraft). In oneimplementation, the service area 104 may be delineated into a pluralityof unit or sub-areas. For example, the service area may be subdividedinto multiple sub-areas of relatively similar area, which may bereferred to as tiles. The size of a tile may be defined, for example,based on degrees of latitude and longitude, such as 1 degree latitudeand 1 degree longitude, or any number of degrees (or a fraction of adegree) of latitude and any number of degrees (or a fraction of adegree) of longitude that are suitable for the service(s) beingprovided. In some implementations, the service area 104 may include allof the Earth's surface or substantially all of the Earth's surface. Inother implementations, the service area 104 may include only a definedportion of the Earth or there may be multiple segregated service areasaround the Earth.

As shown in FIG. 1, multiple satellites 102 (or payloads on board thesatellites) may provide coverage for the service area 104 (or portionsof the service area 104). In some implementations, the footprints ofmultiple individual satellites 102 (or payloads on board suchsatellites) may overlap at least during certain periods of time. In suchcases, the region(s) where the satellites' 102 (or payloads') footprintsoverlap may be covered by multiple satellites 102 (or payloads)concurrently. The number of satellites (or payloads) providing coverageconcurrently for one unit area (e.g., a tile) at a defined point in timeor during a defined period of time may be referred to as the coveragenumber for the unit area at or during that time. Implementations of thepresent disclosure may attempt to provision satellite coverage for anindividual unit area in an effort to ensure that the coverage number forthe unit area at a defined point or during a defined period of time maybe larger than or equal to a specific number required by the service tobe provided for the unit area at or during the defined time, which maybe referred to as the required coverage number for the unit area at orduring the defined time. The required coverage number for a unit area ator during a defined time may be one but may also be a number larger thanone. For example, for air traffic control or surveillance, the requiredcoverage number for a particular unit area at or during a defined timemay be one specific number (e.g., equal to or larger than one); forweather forecasting, the required coverage number may be anotherspecific number (e.g., equal to or larger than one). Moreover, theservice area 104 may be a representative for a plurality of serviceareas that need to be covered by the satellites 102(1), 102(2) and102(3) (or payloads on board the satellites).

In addition to service areas, in certain implementations, there may beone or more areas defined as empty areas and one or more areas definedas nuisance areas on Earth. In such implementations, empty areas may notrequire coverage, but they may be covered with an expectation that therewill be substantially no negative effects for covering them. Nuisanceareas, meanwhile, similarly may not require coverage and they may havenoise sources such that covering them may lower the signal to noiseratio for signals from the service areas received by the satellite(s)102 (or payload(s)) covering such nuisance areas.

In some implementations, a tile may be referred to as being criticallycovered if two conditions are true: there are satellites 102 (orpayloads on board such satellites)) providing coverage for the tile, andthe number of satellites 102 (or payloads on board such satellites)covering the tile is equal to the required coverage number. In suchcases, if a satellite 102 (or payload on board the satellite) providingcritical coverage of a tile is switched off (e.g., so as to not provideservice), the coverage requirement will not be satisfied.

In some implementations, the satellites 102 (or payloads on board thesatellites) may be at least partially solar powered. In suchimplementations, each satellite 102 may have one or more solar panelsthat collect solar energy when exposed to the Sun. The solar panel(s)may convert the solar energy into electrical energy to support operationof the respective satellites (or payloads on board the satellites). Insome implementations, the satellites 102 may include batteries that arecapable of storing electrical energy generated by the solar panel(s) forlater use by the satellites 102. As illustrated in FIG. 1, as asatellite 102(2) orbits the Earth, there may be periods of time duringwhich the satellite 102(2) may be in a shadow of the Earth and, thus,not in a direct line of sight of the Sun. During such periods, thesatellite 102(2) may be referred to as being in eclipse. When asatellite 102 is in eclipse, the solar panels may not generate anyelectrical energy (e.g., because the eclipse condition prevents thesolar panels from receiving solar energy) and the satellite's 102operation may be solely (or largely) supported by battery or some otheralternative energy source and this situation may be taken intoconsideration as described herein.

FIG. 2 illustrates an exemplary system configuration 200 according to animplementation of the present disclosure. As shown in FIG. 2, the system200 may comprise a constellation of satellites 102 (e.g., 102(1),102(2), . . . , 102(n), with n being an integer number equal to orlarger than three), a satellite information repository 202 and acomputing apparatus 204. The satellite information repository 202 may beimplemented as computer (or some other form of electronic) storage andmay store and/or model information related to the satellites 102including operational modes, power consumption levels, and ephemerisdata (e.g., including orbit and eclipse information) for some or all ofthe satellites 102 (or payloads on board some or all of the satellites102) in the constellation. Although shown as separate entities in FIG.2, the satellite information repository 202 may be part of the computingapparatus 204 in some implementations. Moreover, in someimplementations, the satellite information repository 202 may comprisedistributed storage such that portions of the information stored thereinmay be stored across multiple devices, which may be locatedgeographically close (e.g., in the same room or in different buildingsof the same campus) or remote (e.g., in different cities, counties,states, continents, etc.). Regardless of whether the satelliteinformation repository 202 is part of the computing apparatus 204,either or both of the satellite information repository 202 and thecomputing apparatus 204 may be communicatively connected (e.g., eitherdirectly or indirectly) to each of the satellites 102; therefore, thecomputing apparatus 204 may remotely control the satellites 102 (orpayloads on board the satellites 102) for provisioning of the satelliteservice. For example, in some implementations, computing apparatus 204may represent (separately from or together with satellite informationrepository 202) a telemetry, tracking and command (TTAC) ground system.In alternative implementations, satellite information repository 202 andcomputing apparatus 204 may be hosted on or distributed across one ormore of satellites 102 such that the provisioning of the satelliteservice may be wholly or partially controlled by the one or moresatellites 102 (or payloads on board the one or more satellites 102). Asdescribed in greater detail below, computing apparatus 204 may determinewhich of several different operational modes each of the satellites 102(or payloads on board the satellites) should operate in during differentperiods of time and transmit instructions to individual satellites 102(or payloads on the individual satellites) instructing the satellites(or payloads) to enter the determined operational modes for theappropriate time periods.

In one particular example, computing apparatus 204 (separately from ortogether with satellite information repository 202) may represent or becommunicatively coupled to a ground station that establishes wirelesscommunications links (e.g., uplinks and/or downlinks) 206 with one ormore of satellites 102, for instance via electromagnetic signals (e.g.,in the K or K_(a) band). In this example, as the satellites 102 orbit,individual satellites 102 may go in and out of view of the groundstation. Therefore, the ground station may dynamically establish andrelinquish communications links 206 with individual satellites 102 asthe satellites 102 go in and out of view of the ground station. When acommunications link 206 exists between an individual satellite 102 andthe ground station, the ground station may transmit control informationto the satellite 102 via the communications link 206 for use inprovisioning the service. In some cases, such control information may bespecific to the individual satellite 102 (or a payload on board theindividual satellite 102). In other cases, wireless crosslinks 208(e.g., in the K or K_(a) band) may communicatively connect individualsatellites 102 to each other, and the control information transmitted toa satellite 102 by the ground station may be propagated to one or moreor all of the other satellites 102 via the crosslinks 208 for use inprovisioning the service.

In one implementation, all satellites 102 (or individual payloads onboard all of the satellites 102) in the constellation may be configuredto operate within the same set of different modes having the sameaverage (or estimated) power consumption levels as indicated in Table 1below.

TABLE 1 Power Levels Mode Average Power Consumption (in watts “W”) HighOn AA Medium On BB Low On CC High Idle XX Low Idle YY

In such an implementation, each satellite 102 (or an individual payloadon board each satellite 102) may comprise multiple service providingelements. For example, in implementations that provide a surveillanceservice (e.g., a spaced-based ADS-B surveillance service), the serviceproviding elements may be antennas and/or receivers for receiving ADS-Bsignals. Additionally or alternatively, the service providing elementsmay be antennas and/or transmitters or transceivers that are capable oftransmitting signals. When a satellite 102 (or individual payload onboard a satellite 102) is operated in the “High On” mode, all (or arelatively large number) of the service providing elements on thesatellite 102 (or payload on board the satellite 102) may be turned onto provide the coverage and, collectively, these elements may consumepower at the average (or estimated) rate of AA W and provide arelatively high level of coverage within the footprint of the satellite(or payload on board the satellite). For example, when operating in the“High On” mode, the satellite (or the payload on board the satellite),may provide a relatively large number of receive and/or transmit beamswithin the footprint of the satellite (or the payload on the satellite).Consequently, the satellite (or the payload on board the satellite) mayprovide coverage to a relatively large number of tiles within thefootprint of the satellite (or payload on board the satellite) whenoperating in the “High On” mode.

When a satellite 102 (or individual payload on board a satellite 102) isoperated in the “Medium On” mode, a subset of the service providingelements on the satellite 102 (or payload on board the satellite 102)that is less than the service providing elements turned on during the“High On” mode may be turned on to provide the coverage and,collectively, these elements may consume power at the average (orestimated) rate of BB W, which is less than the rate of AA W, andprovide a relatively moderate level of coverage within the footprint ofthe satellite (or payload on board the satellite) that is less than thelevel of coverage when the satellite (or payload on board the satellite)is operated in the “High On” mode. For example, when operating in the“Medium On” mode, the satellite (or the payload on board the satellite),may provide a relatively moderate number of receive and/or transmitbeams within the footprint of the satellite (or the payload on thesatellite) that is less than the number of beams that the satellite (orpayload on board the satellite) provides when operating in the “High On”mode. Consequently, the satellite (or the payload on board thesatellite) may provide coverage to a relatively moderate number of tileswithin the footprint of the satellite (or payload on board thesatellite) that is less than the number of tiles covered when operatingin the “High On” mode.

When a satellite 102 (or individual payload on board a satellite 102) isoperated in the “Low On” mode, a subset of the service providingelements on the satellite 102 (or payload on board the satellite 102)that is less than the service providing elements turned on during the“Medium On” mode may be turned on to provide the coverage and theseelements, collectively, may consume power at an average (or estimated)rate of CC W, which is less than the rate of BB W and provide arelatively low level of coverage within the footprint of the satellite(or payload on board the satellite) that is less than the level ofcoverage when the satellite (or payload on board the satellite) isoperated in the “Medium On” mode. For example, when operating in the“Low On” mode, the satellite (or the payload on board the satellite),may provide a relatively low number of receive and/or transmit beamswithin the footprint of the satellite (or the payload on the satellite)that is less than the number of beams that the satellite (or payload onboard the satellite) provides when operating in the “Medium On” mode.Consequently, the satellite (or the payload on board the satellite) mayprovide coverage to a relatively low number of tiles within thefootprint of the satellite (or payload on board the satellite) that isless than the number of tiles covered when operating in the “Medium On”mode.

When operated in one of the above-described “On” modes, a satellite 102(or payload on board the satellite 102) may be referred to as being in a“functioning” mode (e.g., because the satellite 102 (or payload) iscapable of providing service).

When a satellite 102 (or individual payload on board a satellite 102) isoperated in the “High Idle” mode, all of the service providing elementsmay be turned off and the satellite 102 (or payload), thus, may provideno coverage. Nevertheless, while the satellite 102 (or payload) isoperated in the “High Idle” mode, other circuitry and/or components onboard the satellite 102 (or payload) may still be on and consumingenergy at the average (or estimated) rate of XX W, which is less thanthe rate of CC W. For example, in some implementations, one or moreField Programmable Gate Arrays (FPGAs) may be on board a satellite 102(or payload) (e.g., to provide signal processing functions). In suchimplementations, one or more FPGAs may remain powered on while thesatellite 102 (or payload) is operated in the “High Idle” mode such thatthe FPGA(s) consumes power at an average (or estimated) rate of XX W.The “High Idle” mode may be referred to as a reduced power mode.

When a satellite 102 (or individual payload on board a satellite 102) isoperated in the “Low Idle” mode, all of the service providing elementsand a significant amount of other circuitry and/or components (e.g.,FPGAs) may be turned off. In this mode, the satellite 102 (or payload)may consume power at an average (or estimated) rate of YY W, which isless than XX W, for instance, to keep the system critical circuitryand/or componentry on, such as, for example, the system timer, hardwaresetting, etc. In some implementations, the “Low Idle” mode may be the“off” mode but with the system critical circuitry on, such that thesatellite may be remotely turned on. When operated in the “High Idle”mode or the “Low Idle” mode, a satellite 102 (or payload on board thesatellite 102) may be referred to as being in a “non-functioning” mode(e.g., because the satellite 102 (or payload) is not capable ofproviding service).

In another implementation, the satellites 102 (or individual payloads onboard of the satellites 102) in the constellation may not necessarily beconfigured to operate within the same set of different modes having thesame average (or estimated) power consumption levels. For example, afirst subset of the satellites 102 (or payloads on board the firstsubset of satellites 102) in the constellation may be configured tooperate in the modes depicted in Table 1, but another subset of thesatellites 102 (or payloads on board the second subset of satellites102) in the constellation may be configured to operate in three modes:“On” with an average (or estimated) power consumption rate of AA1 W;“High Idle” with an average (or estimated) power consumption rate of XX1W, which is less than a rate of AA1 W; and “Idle” or “Off” with anaverage (or estimated) power consumption rate of YY1 W, which is lessthan a rate of XX1 W.

Regardless of whether the satellites 102 (or individual payloads onboard the satellites 102) in the constellation are configured to operatein the same modes, the satellite information repository 202 may storepower consumption information for the different operational modes of allsatellites 102 (or payloads on board the satellites 102) in theconstellation. Each symbol referenced above in connection with powerconsumption levels, e.g., “AA,” “BB,” “CC,” “XX,” “YY,” “AA1,” “XX1,”and “YY1,” may represent a numerical value of a power consumption rate,which, for example, may be obtained by circuit design data or asempirical data among other approaches. It should be appreciated that atleast one or more satellites (or payloads or board such satellites) inone implementation may have two “on” modes or more than three “on” modesand the respective power consumption level for each “on” mode may beused for the satellite (or payload) coverage provisioning processaccordingly.

The computing apparatus 204 may provision the satellite coverage basedon the information in the satellite information repository 202 and/orother information. In provisioning the satellite coverage, certainconstraints (or other factors) may be taken into account. For example, afirst time-related constraint may be that the total power consumption byan individual satellite 102 (or payload on board the individualsatellite 102) during a defined sliding time window of length T_(w) beless than some first defined maximum amount, and a second time-relatedconstraint may be that the total power consumption by the satellite (orpayload on board the satellite) during an eclipse period be less thansome second defined maximum amount. In some implementations, the slidingwindow of time (T_(w)) may be the same duration as the satellite orbitperiod (e.g., ˜100 minutes for a satellite at an 800 km altitude). Inone implementation, the computing apparatus 204 may provision thesatellite coverage according to a greedy algorithm that seeks tominimize the power consumption for each individual satellite 102 (or apayload on board each individual satellite) rather than focusing on thetotal power consumption of the satellites 102 (or payloads on board thesatellites) in the constellation in the aggregate.

Additionally or alternatively, irrespective of other factors, thecomputing apparatus 204 may determine to turn an individual satellite102 (or payload on board the individual satellite 102) off (e.g., put itinto a “High Idle” or “Low Idle” mode) in response to determining (i)that the total cumulative power consumption by the satellite (or payloadon board the satellite) at any point during a defined time period (e.g.,T_(w)) will or has exceeded a defined power consumption threshold level,or (ii) the total cumulative power consumption by the satellite 102 (orpayload on board the satellite 102) during an eclipse period will or hasexceeded a defined eclipse period power consumption threshold level. Anexample of how an individual satellite (or payload on board a satellite)may be powered on and off (e.g., switched between a functional mode anda non-functional mode) according to a power consumption constraint isshown in FIG. 3, which illustrates a hysteresis for cumulative powerconsumption during a sliding window of time (e.g., T_(w)) for asatellite (or payload on board the satellite) according to animplementation. As shown in FIG. 3, a cumulative power consumption curve302 may represent the (actual or projected) cumulative power consumptionfor one satellite (or a payload on board the satellite) over slidingwindow period T_(w). Two cumulative power consumption threshold valuesmay be defined: Q_(off) and Q_(on). The threshold values Q_(off) andQ_(on) may not be absolute values; instead, they may represent thresholdvalues within a sliding time window of the length T_(w). The thresholdQ_(off) may designate a cumulative power consumption value during theperiod T_(w) that, if reached (or projected to be reached) by thesatellite (or payload on board the satellite) causes the satellite (orpayload on board the satellite) to be turned off, e.g., transitioningthe satellite (or payload on board the satellite) into the “High Idle”or “Low Idle” mode. In some implementations, the power consumption inthe “High Idle” mode may be too large to give any benefit when and if anemergency hits. Therefore, in these implementations, the satellite (orpayload on board the satellite) may be transitioned to the “Low Idle”mode when Q_(off) is exceeded (or projected to be exceeded) duringT_(w), and the “Low Idle” mode may be referred to as an “emergency mode”or “minimal energy consumption” mode. In the case where a satellite (orpayload on board the satellite) has been placed in a lower power modesuch as an “emergency mode,” the satellite (or payload on board thesatellite) can be restored to a higher power mode (e.g., one of the“High On,” “Medium On,” “Low On,” or “High Idle” modes) in response tothe cumulative power consumption within the sliding time window falling(or projected to fall) to a cumulative power consumption thresholdQ_(on) that is less than the cumulative power consumption thresholdQ_(off). It should be appreciated that FIG. 3 shows an example of asituation in which a satellite (or payload on board a satellite) turnson, keeps consuming power until its cumulative power consumption withina sliding window of time hits Q_(off) and is turned off (or turned to areduced power consumption mode), but, after some time, its cumulativepower consumption during the sliding window of time goes down and fallsto Q_(on) and is turned on again (or returned to a higher powerconsumption mode) in response. In various scenarios, however, the(actual or projected) cumulative power consumption curve of a satellite(or a payload on the satellite) may go up and down between the twothreshold values Q_(off) and Q_(on) over time without necessarilyreaching either threshold value.

Having two cumulative power consumption threshold values Q_(off) andQ_(on), respectively, essentially provides hysteresis that prevents thesatellite (or payload on board the satellite) from frequently togglingbetween higher and lower power consumption modes. For example, if asatellite (or payload on board a satellite) is in a higher powerconsumption mode over a significant period of time, it is possible thecumulative power consumed within the sliding time window at some pointmay exceed (or be projected to exceed) the threshold Q_(off), causingthe satellite (or payload on board the satellite) to enter a lower powerconsumption mode. Once in the lower power consumption mode, thecumulative power consumed during the sliding time window may diminishbelow the cumulative power consumption threshold Q_(off), but thesatellite (or payload on board the satellite) may not be restored to ahigher power consumption mode until the cumulative power consumed (orprojected to be consumed) during the sliding time window diminishes tothe lower cumulative power consumption threshold Q_(on). Thereafter, thesatellite (or payload on board the satellite) may then remain in thehigher power consumption mode until the cumulative power consumed (orprojected to be consumed) during the sliding time window again exceeds(or is projected to exceed) the higher cumulative power consumptionthreshold Q_(off).

In some implementations, the hysteresis for cumulative power consumptionshown in FIG. 3 may not be employed when a satellite is in an eclipseperiod. In one implementation, if a satellite (or payload on board thesatellite) is put into an emergency mode during an eclipse period, thesatellite (or the payload on board the satellite) may be retained in theemergency mode until the eclipse period ends.

In an effort to keep the power consumption of an individual satellite(or payload on board the satellite) as low as possible, the computingapparatus 204 may implement features as follows:

-   -   1) Keep track of the cumulative power consumption (e.g., actual        or projected) in a current sliding time window (the cumulative        eclipse power consumption may be tracked separately) and turn        the satellite (or payload on board the satellite) to the “Low        Idle” mode in response to detecting that the satellite (or the        payload on board the satellite) has hit (or is projected to hit)        its emergency threshold.    -   2) While the satellite (or payload on board the satellite) is        operating in an operational mode, aggressively try to switch the        satellite (or payload on board the satellite) to a lower power        consumption mode (e.g., the “High Idle” mode) whenever the        satellite (or payload on board the satellite) does not provide        critical coverage to any tile within its footprint (or any tiles        expected to be within its footprint during a defined period of        time). For example, if all of the tiles within the satellite's        (or payload's) footprint (or expected to be within its footprint        during a defined period of time) are more than critically        covered, the satellite(s) (or payload(s) on board the        satellite(s)) with larger cumulative power consumption (or        projected power consumption) and/or eclipse power consumption        may be switched to the “High Idle” mode.    -   3) After the satellite (or the payload on board the satellite)        has operated in the “High Idle” mode for a defined period of        time, switch the satellite (or payload on board the satellite)        to the “Low Idle” mode.

Additionally or alternatively, in some implementations, a periodic oraperiodic reboot of the satellite (or the payload on board thesatellite) may be planned as part of the satellite (or payload)provisioning process. This may be provided, for example, to satisfy asatellite (or payload) requirement, which may require a reboot at leastonce per orbit period (e.g., to support thermal dissipation). In someimplementations, the reboot may be performed when the satellite is in anon-functional mode. In at least one implementation, the provisioningprocess may define a maximal waiting time for the satellite (or payloadon board the satellite) since the last time the satellite (or payload onboard the satellite) was operated in a non-functional mode (T_(wait)),and switch the satellite (or payload on board the satellite) to anon-functional mode at least once after (or during) such maximal waitingtime.

FIG. 4 illustrates a flow diagram of an exemplary satellite coverageprovisioning process 400 according to an implementation of the presentdisclosure. In some implementations, the process may be performed by orin conjunction with a computing apparatus such as, for example,computing apparatus 204 of FIG. 2 and/or a computing apparatus on boarda satellite. The satellite coverage provisioning process 400 may startat block 402, at which power consumption states for satellites (orpayloads on board the satellites) within a constellation of satellitesmay be updated. In some implementations, information about the powerconsumption states of the satellites (or payloads on board thesatellites) may be stored in a satellite information repository, suchas, for example, satellite information repository 202. The powerconsumption state of each satellite (or a payload on the satellite) mayinclude without limitation the satellite's (or payload's) current powerconsumption information, historical power level information (e.g.,cumulative power consumption during a sliding window of time), currentoperational mode, and/or projected future power consumption.

At block 404, whether each satellite (or a payload on each satellite) ofthe constellation of satellites is required to be in a minimal energyconsumption mode (e.g., the “Low Idle” mode) may be determined, forexample, based on the updated power consumption state of the satellite(or the payload on board the satellite) and/or other factors. Forexample, it may be determined whether the cumulative power consumptionof the satellite (or a payload on board the satellite) during a slidingwindow of time exceeds a first threshold value and/or whether thecumulative power consumption of the satellite (or a payload on thesatellite) during an eclipse period exceeds a second threshold value. Insome implementations, this determination may be based, at least in part,on projected future power consumption. For example, if the projectedfuture power consumption of the satellite (or a payload on board thesatellite) during a defined future time period suggests that thecumulative power consumption of the satellite (or payload on board thesatellite) during a sliding window of time that includes at least aportion of the defined future time period will exceed a definedthreshold value, a determination may be made that the satellite (orpayload on board the satellite) is required to be in a minimal energyconsumption mode. Each satellite (or payload on board the satellite)determined to be required to be in a minimal energy consumption modethen may be controlled to be transitioned to the minimal energyconsumption mode. For example, a signal may be sent to the satellite (orthe payload on the satellite) instructing the satellite to transition tothe minimal energy consumption mode.

At block 406, for each satellite of the constellation of satellites (ora payload on each satellite of the constellation of satellites) that isnot required to be in the minimal power consumption mode, a powerconsumption score may be calculated. The power consumption score may bea numerical value representing how close the satellite's (or payload's)cumulative power consumption in a sliding time window is to a limit(e.g., the maximal allowable power consumption during the sliding timewindow). In some implementations, the power consumption score for asatellite (or payload on board the satellite) may be based on historicpower consumption by the satellite (or payload on board the satellite).Additionally or alternatively, in some implementations, the powerconsumption score for a satellite (or payload on board the satellite)may be based, at least in part, on projected future power consumption bythe satellite (or payload on board the satellite). In oneimplementation, a satellite (or a payload on board the satellite) havinga higher power consumption score may be closer to the maximal allowablecumulative power consumption threshold than a satellite (or payload onboard the satellite) having a lower power consumption score. Asdescribed herein, in some implementations, the power consumption scoremay be calculated by taking into consideration whether the satellite (orpayload on board the satellite) is in an eclipse period. Moreover, insome implementations, inputs used in calculating the power consumptionscore for a satellite (or a payload on board the satellite) may beretrieved from a satellite information repository, such as, for example,satellite information repository 202 of FIG. 2

At block 408, the satellites (or payloads on the satellites) that arenot required to be in the minimal power consumption mode may be sortedaccording to their respective power consumption scores. At block 410,the satellite coverage provisioning process 400 may determine, based onrespective power consumption scores of the satellites (or payloads onthe satellites) and coverage of the service area, whether each of thesatellites (or payloads on board the satellites) that are not requiredto be in the minimal power consumption mode can be put into a reducedpower mode (e.g., the “High Idle” mode). For example, in someimplementations, starting with the satellite (or payload on thesatellite) closest to the maximal power consumption threshold, adetermination may be made, based on the current operational modes of thesatellites in the constellation and other information stored in thesatellite information repository 202 (e.g., satellite (or payload)ephemeris), as to whether all of the tiles in the footprint of thesatellite (or payload on board the satellite) (or expected to be withinthe footprint of the satellite (or payload on board the satellite)within a defined period of time) requiring coverage are (or will be)critically covered or more than critically covered. If the result isaffirmative and transitioning the satellite (or payload on board thesatellite) to a reduced power mode will not result in any of the tilesrequiring coverage dropping below a critical coverage level, it may bedetermined to transition the satellite (or payload on board thesatellite) to a reduced power mode. This determination thereafter may berepeated in order for each of the satellites (or payloads on board thesatellites) in the sorted list. As described above, in someimplementations, the satellites (or payloads on board the satellites)may be configured to operate in one of multiple different functionalmodes (e.g., “High On,” “Medium On,” and “Low On”). In suchimplementations, a particular functional mode for each satellite (orpayload on board the satellite) not determined to be switched into thereduced power mode may be determined, for instance, based on theconsumption score and coverage of the service areas. For example, ahigher power consumption mode may be selected for a satellite (orpayload on board the satellite) when the power consumption score isrelatively low and/or the required coverage of the service area isrelatively high than when the power consumption score is relatively highand/or the required coverage of the service area is relatively low.

At block 412, whether each satellite (or payload on board the satellite)of the constellation of satellites that is in a reduced power mode(e.g., the “High Idle” mode) can be put into a minimal energyconsumption (e.g., the “Low Idle” mode) mode may be determined. In someimplementations, it may be determined that a satellite (or payload onboard the satellite) can be put into the minimal energy consumption modeafter the satellite (or payload on board the satellite) has beenassigned to the reduced power mode for some defined number ofconsecutive schedule slots. The satellites (or payloads on thesatellites) for which determinations were made to transition todifferent operating modes (e.g., into the “High Idle” or “Low Idle”modes) then may be instructed to be transitioned to the appropriateoperating modes. For example, signals may be sent to each satellite (orthe payload on the satellite) instructing the satellite to transition tothe appropriate operating mode. Additionally or alternatively, in someimplementations, process 400 may be performed in advance in order togenerate a provisioning schedule for each satellite that then isuploaded to each satellite, for example, via uplinks 206. For example,future provisioning schedules for each satellite may be generated morethan twenty-four hours (or more) out. These provisioning schedules (orportions of these provisioning schedules) then may be uploaded to eachsatellite. In some implementations, each schedule slot (e.g., possiblenew operational state) may be 30 seconds, and new provisioning schedulesmay be uploaded to the satellites every 120 seconds (or, in someimplementations, more or less frequently). Each individual satellitethen may adjust its operating mode in accordance with the appropriateprovisioning schedule.

An exemplary satellite coverage provisioning process according to thepresent disclosure may implement a greedy algorithm that seeks tominimize power consumption of individual satellites (or payloads onindividual satellites) instead of global power consumption across theconstellation in the aggregate. In one implementation, the greedyalgorithm may be implemented as a repeating loop with an incrementaltime step Δt_(s). This incremental time step Δt_(s) and examples of anumber of other configuration parameters, which may be stored, forexample, in satellite information repository 202 or otherwise accessibleby computing apparatus 204, are listed in Table 2 below.

TABLE 2 Exemplary Configuration Parameters for Satellite CoverageProvisioning Parameter Description Δt_(s) Calculation incremental timestep P_(High) Power consumption level in “High On” mode P_(Medium) Powerconsumption level in “Medium On” mode P_(Low) Power consumption level in“Low On” mode P_(aver) Average power consumption level when not in “HighIdle” or “Low Idle” mode P_(high.idle) Power consumption level in “HighIdle” mode P_(idle) Power consumption level in “Low Idle” mode T_(w)Sliding window of time from (t − T_(w)) to t, where t is the currenttime (the time being scheduled). Q_(off) Emergency threshold forcumulative power consumption in T_(w) Q_(on) Cumulative powerconsumption in T_(w) threshold for coming out of the emergency mode,Q_(on) < Q_(off) Q_(max.eclipse) Emergency cumulative power consumptionthreshold during eclipse period T_(idle) Minimum time satellite (orpayload on satellite) remains in “Low Idle” mode after transitioninginto “Low Idle”, in minutes T_(wait) Minimum time since satellite (orpayload on satellite) was last in “Low Idle” mode before satellite (orpayload on satellite) can return to “Low Idle” mode, in minutesT_(reboot) Maximal waiting time since the last reboot, in minutes αWeighting parameter for scoring power consumption during an eclipseperiod

Most parameters in Table 2 have been explained above and/or will beexplained in detail below. The quantities measured in Watts may bedenoted as P with a respective subscript and the quantities measured inWatt-minutes as Q with a respective subscript.

As described above, in some implementations, service requirements maydictate a reboot (e.g., of the satellite, a payload on board thesatellite, and/or certain componentry on board the satellite or on apayload) at least once per orbit (e.g., to support thermal dissipation).Thermal dissipation may be particularly applicable for FPGAs and otherelectronics in space due to accumulation of cosmic radiation and itsimpact on gate logic and signal processing while in operation. Thus, inaddition to the other features already explained above, at least onereboot of the satellite (or payload on board the satellite) per orbitmay be planned as part of the satellite coverage provisioning process.As indicated by the parameter T_(reboot) in Table 2, the maximal waitingtime since the last reboot may be defined. In some implementations, thereboot may be done whenever the satellite (or payload on board thesatellite) is in the “Low Idle” (or “High Idle”) mode (e.g., upon thesatellite (or payload on board the satellite) transitioning into the“Low Idle” (or “High Idle”) mode). In at least one implementation, thesatellite coverage provisioning process may define a maximal waitingtime since the last “Low Idle” (or “High Idle”) mode (T_(reboot)) andreboot a satellite (or payload on board the satellite) at least onceafter (or during) such maximal waiting time. In other words, if theconfigured time period T_(reboot) elapses without the satellite (orpayload on board the satellite) having been rebooted, the satellitecoverage provisioning process may cause the satellite (or payload onboard the satellite) to enter the “Low Idle” (or “High Idle”) mode andreboot. Alternatively, in some implementations, if the configured timeperiod T_(reboot) elapses without the satellite (or payload on board thesatellite) having been rebooted, the satellite coverage provisioningprocess may schedule the satellite (or payload on board the satellite)to enter the “Low Idle” (or “High Idle”) mode and reboot at the nextopportunity determined to be convenient to do so.

In addition to the configuration parameters listed in Table 2, examplesof information about the current and previous states of the satellites(or payloads on board the satellites) and other information potentiallyrelevant to the satellite coverage provisioning, which may be stored,for example, in satellite information repository 202 or otherwiseaccessible by computing apparatus 204, are listed in Table 3 below.

TABLE 3 Exemplary Information Stored Per Satellite (or Payload On BoardSatellite) for Satellite Coverage Provisioning Process ParameterDescription Q_(total) Cumulative power consumption during the slidingwindow, initialized to zero C_(i) Array of power consumption data withT_(w)/Δt_(s) entries, C₀ corresponds to the most recent step, C₁ to theprevious one etc. Initialized to zero. Q_(eclipse) Cumulative powerconsumption since beginning of an eclipse period, initialized to zeroEMERGENCY Flag whether the satellite is in the emergency mode. ECLIPSEFlag whether the satellite is in an eclipse period. It may be setexternally based on the ephemerides t_(eclipse.left) If the satellite isin an eclipse period, the time until the end of the current eclipseperiod, otherwise undefined. M Current operational mode M_(p) Previousoperational mode t_(on) Last time satellite (or payload on boardsatellite) came off a “High Idle” operational mode, in minutes S Powerconsumption score

The quantities related to power in Table 3 may be measured in eitherWatt-minutes or average Watts, as long as the choice is the same for theactual consumption and the threshold values.

As described above, power consumption scores (denoted as S in Table 3)may be calculated for individual satellites (or payloads on board thesatellites). In one implementation, when a satellite (or payload onboard the satellite) is not in an eclipse period, the power consumptionscore for the satellite (or payload on board the satellite) may becalculated as a ratio of the cumulative power consumption Q_(total) inthe sliding window (T_(w)) to the maximal (e.g., emergency) energyconsumption threshold Q_(off).

S=Q _(total) /Q _(off)  (1)

In some implementations, when a satellite (or payload on board thesatellite) is in an eclipse period, its cumulative power consumptionuntil the end of the eclipse period is desired to be less than a maximaldefined value during the eclipse period, which may be the configurationparameter “Emergency cumulative power consumption threshold duringeclipse period” denoted as Q_(max.eclipse) in Table 2. If the satellite(or payload on board the satellite) remains in one of the “on” modesuntil the end of the eclipse period, its cumulative power consumptionduring the eclipse period may be equal to the cumulative powerconsumption since the beginning of the eclipse period (e.g., Q_(eclipse)in Table 3) plus future spending (e.g., t_(eclipse.left) multiplied by apower consumption rate P, where t_(eclipse.left) has been defined inTable 3 and P may be one of P_(High), P_(Medium), or P_(Low) as definedin Table 2). The time t_(eclipse.left) may be calculated based on thesatellite's orbit, travel scheduling information and the Sun's position,any or all of which, for example, may be stored in satellite informationrepository 202 or otherwise available to computing apparatus 204. In oneimplementation, the average energy consumption P_(aver) may be used forP. A power deficiency variable Q_(deficiency) may be calculated as:

Q _(deficiency)=(Q _(eclipse) +t _(eclipse.left) P)Q _(max.eclipse)  (2)

As for calculating the power consumption score of a satellite (or apayload on board the satellite) in an eclipse period, a ratio of thisdeficiency to Q_(max.eclipse) may be calculated as:

$\begin{matrix}{S_{eclipse} = \left\{ \begin{matrix}{0,} & {Q_{deficiency} \leq 0} \\{{Q_{deficiency}\text{/}Q_{\max.{eclipse}}},} & {Q_{deficiency} > 0}\end{matrix} \right.} & (3)\end{matrix}$

Then the power consumption score for the satellite (or a payload onboard the satellite) with eclipse adjustment may be calculated as:

$\begin{matrix}{S = \left\{ \begin{matrix}{S_{normal},} & {{Not}\mspace{14mu} {in}\mspace{14mu} {eclipse}} \\{{S_{normal} + {\alpha \; S_{eclipse}}},} & {{In}\mspace{14mu} {eclipse}}\end{matrix} \right.} & (4)\end{matrix}$

The parameter α in the equation (4) may represent the importance of theeclipse constraint. For example, by increasing the parameter α, theexemplary satellite coverage provisioning process may be more aggressivein switching off satellites (or payloads on board the satellites) ineclipse periods. In some implementations, the parameter α may bedetermined based on simulation. In one non-limiting implementation, theparameter α may be selected as α≈0.1. Other values for α may also beused in different implementations.

FIG. 5 illustrates an exemplary iteration 500 of a loop for satellitecoverage provisioning using a constellation of satellites (or payloadson board a constellation of satellites). In some implementations, theiteration 500 may be performed by or in conjunction with a computingapparatus such as, for example, computing apparatus 204 of FIG. 2 and/ora computing apparatus on board a satellite. The iteration 500 may beperformed for each satellite (or a payload on board each satellite) foran incremental time step Δt_(s). One example Δt_(s) may be a valuebetween 5-30 s depending on the orbital altitude/velocity and thedesired accuracy of the coverage information. The iteration 500 maystart at 502. At operation 504, the iteration 500 may prepare eachsatellite (or payload on board each satellite) in the constellation ofsatellites. In one implementation, the operation 504 may include, foreach of the satellites (or a payload on board each of the satellites) inthe constellation, updating stored information about the current and/orpast operational modes of the satellite (or payload on board thesatellite), updating stored information about the current and/or pastpower consumption of the satellite (or payload on board the satellite),checking whether to remain in or enter emergency mode, and (if not in orentering emergency mode) calculating the power consumption score. Insome implementations, as part of operation 504, satellites (or payloadson board the satellites) for which it is determined to enter theemergency mode may be scheduled or instructed to enter the emergencymode. As described herein, a power consumption score for each satellite(or a payload on board each satellite) may be calculated withconsideration of whether the satellite (or payload on board thesatellite) is in an eclipse period. One exemplary implementation of theoperation 504 may be a subroutine or sub-process which may be invoked bythe iteration 500. A flowchart illustrating such a sub-process is shownin FIG. 6 and will be described below.

At operation 506, for each satellite (or payload) that is in emergencymode (e.g., its EMERGENCY variable being true), the critically coveredtiles by such a satellite (or payload) during a defined future timeperiod (e.g., Δt_(s)) while the satellite (or payload) remains inemergency mode may be added to a bad tiles list. As described above, atile is critically covered if the number of satellites (or payloads)providing coverage of the tile is equal to the required number toprovide the coverage. If a satellite (or payload on board the satellite)is in emergency mode, its service providing elements are turned off andthus, the satellite (or payload on board the satellite) cannot providecoverage. Therefore, any tiles being critically covered with coverageprovided by the satellite (or payload on board the satellite) while thesatellite (or payload) is in emergency mode is now not sufficientlycovered. The bad tiles list may be used to keep track of tiles that haveeither no coverage or a shortage in the required or desired coverage.Ephemeris data for each satellite (or payload on board the satellite)(e.g., the projected orbit and corresponding footprint of the satellite(or payload) during the future time period) may be used in identifyingbad tiles during the future time period.

At operation 508, the iteration 500 may sort satellites (or payloads onboard the satellites) not determined to remain in or enter the emergencymode (e.g., in operation 504) into an array (e.g., denoted N) ordered bytheir respective power consumption scores. The power consumption scoresmay have been calculated as part of the sub-process for preparation ofeach satellite in operation 504. In one implementation, the satellites(or payloads on board the satellites) may be arranged in the array in adescending order such that, in the next two operations, the satellites(or payloads on board the satellites) having higher power consumptionscores may be processed earlier than those having lower powerconsumption scores. In some cases, two or more satellites (or payloadson board the satellites) may have equal power consumption scores. Insuch cases, satellites (or payloads on board the satellites) may besorted first based on their power consumption scores and then based onone more additional attributes. At operation 510, the iteration 500 mayiterate through the satellites (or payloads on board the satellites) inthe array and determine whether each satellite (or payload on board thesatellite) may be put into “High Idle” mode. Satellites (or payloads onboard the satellites) for which it is determined to enter the “HighIdle” mode may be instructed or scheduled to enter the “High Idle” mode.At operation 512, the iteration 500 may iterate through the satellites(or payloads on board the satellites) that already have been determinedto be in or to enter the “High Idle” mode and determine whether eachsuch satellite (or payload on board the satellite) may be put into “LowIdle” mode. Satellites (or payloads on board the satellites) for whichit is determined to enter the “Low Idle” mode may be instructed orscheduled to enter the “Low Idle” mode. Each of operation 510 andoperation 512 may be implemented in a subroutine or sub-process whichmay be invoked by the iteration 500. A flowchart illustrating asub-process for operation 510 is shown in FIG. 8 and a flowchartillustrating a sub-process for operation 512 is shown in FIG. 9.According to at least one implementation of the satellite coverageprovisioning process, the higher the energy consumption score, the moreurgent it is to switch off the satellite.

FIG. 6 illustrates an exemplary sub-process 600 for preparing eachsatellite (or a payload on board each satellite). In one implementation,the sub-process 600 may be invoked at operation 504 at least once foreach satellite (or a payload on board each satellite) in theconstellation of satellites separately. The sub-process 600 may start at602. At operation 604, the sub-process 600 may update variables for thesatellite (or a payload on board the satellite) currently beingprocessed. One exemplary implementation of the operation 604 may beimplemented in a subroutine or sub-process which may be invoked atoperation 604. A flowchart illustrating such a sub-process is shown inFIG. 7 and will be described below.

At operation 606, the previous operational mode for the satellite (orpayload on board the satellite) currently being processed may be stored.As indicated in Table 3, a current operational mode may be denoted as Mand a previous operational mode may be denoted as M_(p) (“current” maybe in the sense of being processed, not necessarily the operational modecontemporaneous with execution of the operation 606). Thus, for example,operation 606 may be implemented as an assignment, such as M_(p)=M insome common programming languages (e.g., C/C++, Java, FORTRAN, etc.). Atoperation 608, whether the EMERGENCY variable is true and whetherQ_(total) is larger than or equal to Q_(on) may be determined. If bothconditions are true, the sub-process 600 may proceed to block 610, atwhich the current operational mode may be assigned to “Low Idle,” andthen the sub-process 600 may end at block 612. (Unless indicatedotherwise, the “end” blocks in FIGS. 6-9 may be implemented as a“return” in many common programming languages). In one implementation,operation 610 may be used to continue the emergency mode for thesatellite (or payload on board the satellite) currently underprocessing. In some implementations, after a determination is made thata satellite (or payload on board a satellite) should stay in or enterthe “Low Idle” mode, the satellite (or payload on board the satellite)may be instructed or scheduled to stay in or enter the “Low Idle” modeaccordingly. If either or both conditions “EMERGENCY variable is true”or “Q_(total) is larger than or equal to Q_(on)” are not true, thesub-process 600 may proceed to block 614, at which whether the ECLIPSEvariable is true and whether the previous state is eclipse may bedetermined. If both conditions are true in block 614, the sub-process600 may proceed to block 616, at which the EMERGENCY flag may becleared. In one implementation, the operation 616 may be used toindicate that the satellite (or payload on board the satellite)currently being processed is coming out of an eclipse period. If eitheror both conditions are false in block 614, or alternatively, after theoperation 616, the sub-process 600 may proceed to block 618, at whichwhether Q_(total) is larger than or equal to Q_(off) may be determined.If Q_(total) is larger than or equal to Q_(off), the sub sub-process 600may proceed to block 620, at which the satellite (or payload on boardthe satellite) may be put into the “Low Idle” mode for energyconsumption and its EMERGENCY variable set as true. From block 620, thesub-process 600 may end at block 624. If, however, Q_(total) is lessthan Q_(off), the sub-process 600 may proceed to block 622, at whichwhether ECLIPSE is true and Q_(eclipse) is larger than or equal toQ_(max.eclipse) may be determined. If ECLIPSE is true and Q_(eclipse) islarger than or equal to Q_(max.eclipse), the sub-process 600 may proceedto block 620. If ECLIPSE is not true, Q_(eclipse) is less thanQ_(max.eclipse), or both, the sub-process 600 may proceed to block 626,at which the EMERGENCY variable may be assigned to false. Operation 626may indicate that the satellite (or payload on board the satellite)currently being processed is not in the emergency mode, if thesub-process 600 reaches this block.

From block 626, the sub-process 600 may proceed to block 628, at whichthe predicted cumulative power consumption for the satellite (or payloadon board the satellite) may be calculated. As described above, thepredicted cumulative power consumption may be calculated based on theoperational modes of the satellite (or payload on board the satellite)and predicted time periods in the different operational modes. At leastin one implementation, this calculation may use the average powerP_(aver) to calculate the predicted cumulative power consumption.Regardless of whether using specific power for the specific power modes(e.g., P_(High), P_(Medium), or P_(Low)) or using the average powerP_(aver), this operation 626 may be implemented in a separate subroutineor sub-process in some implementations.

From block 628, the sub-process 600 may proceed to block 630, at whichthe power consumption score may be calculated (e.g., using equation (1)and the predicted cumulative power consumption). At block 632, whetherECLIPSE is true may be determined. If the satellite (or payload on boardthe satellite) currently being processed is in an eclipse period, theresult of operation 632 may be “YES,” and the sub-process 600 mayproceed to block 634. At 634, the power consumption score may beadjusted for the eclipse condition. As described above, the powerdeficiency variable Q_(deficiency) may be calculated according toequation (2) and the predicted cumulative power consumption, then ascoring parameter for eclipse S_(eclipse) as a ratio of this deficiencyto Q_(max.eclipse) may be calculated according to equation (3), and thetotal power consumption score adjusted for eclipse may be calculatedaccording to equation (4). From block 634, the sub-process 600 mayproceed to block 636 and end. If the satellite (or payload on board thesatellite) currently being processed is not in an eclipse period, theresult of operation 632 may be “NO,” and the sub-process 600 may alsoproceed to block 636 and end.

FIG. 7 illustrates an exemplary sub-process 700 for updating theoperational status of each satellite (or a payload on board eachsatellite). In one implementation, the sub-process 700 may be invoked atoperation 604. The sub-process 700 may start at block 702. At block 704,whether the current operational mode is neither “Low Idle” nor “HighIdle” may be determined. If operation 704 returns “YES,” the sub-process700 may proceed to 706, at which the current time may be assigned to thevariable t_(on). This operation may represent storing the time that thesatellite leaves the idle mode. If operation 704 returns “NO,” or theoperation at block 706 has finished, the sub-process 700 may proceed toblock 708, at which a current power consumption level may be assigned toa variable P (e.g., based on the operational mode of the satellite (orpayload on board the satellite). For example, if the satellite (orpayload on board the satellite) is in (or during the time period Δt_(s)will be in) one of the operational modes, the variable P may be assigneda value of P_(High), P_(Medium), or P_(Low) as appropriate given theoperational mode of the satellite (or payload on board the satellite).Alternatively, if the satellite (or payload on board the satellite) isin (or during the time period Δt_(s) will be in) one of the operationalmodes, the variable P may be assigned a value of P_(aver). Then at block710, the cumulative power consumption Q_(total) may be calculated as aprevious value of Q_(total) plus (P−C_(last)) multiplied by Δt_(s), thearray C may be shifted by one, and the value of the variable P may beassigned to C₀. This process associated with array C creates the“sliding window” effect in an iterative way by updating Q_(total). Atblock 712, whether the satellite (or payload on board the satellite) isin an eclipse period may be determined by checking whether the ECLIPSEvariable is true. If the satellite (or payload on board the satellite)is in an eclipse period, the cumulative power consumption since thebeginning of the eclipse Q_(eclipse) may be updated at block 714 toaccount for the power consumed during the incremental time step Δt_(s)such that Q_(eclipse)=Q_(eclipse)+P×Δt_(s), and the sub-process 700 mayend at block 718. If the satellite (or payload on board the satellite)is not in an eclipse period, the power consumption since the beginningof the eclipse period Q_(eclipse) may be set to zero at block 716, andthe sub-process 700 may end at block 718.

FIG. 8 illustrates an exemplary sub-process 800 for determining whethera satellite (or a payload on board the satellite) (e.g., a satellite (ora payload on board the satellite) not in emergency mode) may be put intoa “High Idle” operational mode. In one implementation, the sub-process800 may be invoked at operation 510. The sub-process 800 may start atblock 802. At block 804, whether all tiles covered by the satellite (orpayload on board the satellite) currently being processed are criticallycovered (or will be critically covered during a future time period(e.g., Δt_(s)) may be determined. If operation at block 804 returns“YES,” that means the satellite (or payload on board the satellite)currently being processed provides (or will provide) redundant coveragefor tiles it covers and thus, the satellite (or payload on board thesatellite) currently being processed may be put to “High Idle” mode atblock 806. That is, the satellite (or payload on board the satellite)currently being processed may be configured to stop the coverage. Ifoperation at block 804 returns “NO,” or alternatively, after the block806, the sub-process 800 may end at block 808.

FIG. 9 illustrates an exemplary sub-process 900 for determining whethera satellite (or payload on board the satellite) (e.g., a satellite (orpayload on board the satellite) that is scheduled for “High Idle” mode)may be put into the “Low Idle” operational mode. In one implementation,the sub-process 900 may be invoked at operation 512. The sub-process 900may start at block 902. At block 904, whether the current mode for thesatellite (or payload on board the satellite) currently being processedis in “High Idle” mode may be determined. If operation at block 904returns “NO,” the sub-process 900 may end at block 906. If operation atblock 904 returns “YES,” the sub-process 900 may proceed to block 908,at which the number of previous consecutive “High Idle” periods may beassigned to a variable N_(high.idle). Each previous “High Idle” periodmay be for an incremental time step Δt_(s).

Then at block 910, whether to reboot the satellite (or payload on boardthe satellite) currently being processed may be determined. As describedabove, certain services may require a satellite (or a payload on boardthe satellite) to be rebooted during a certain period of time, such asone orbit, for example. In one implementation, the condition fordetermining whether to reboot may be whether the current timeT_(current.time) minus the last time the satellite (or payload on boardthe satellite) came off Low Idle mode T_(on) is larger than apre-defined maximal waiting time value since the last reboot T_(reboot)(e.g., checking whether T_(current.time)−T_(on)>T_(reboot)). Ifoperation 910 returns “NO,” at block 914, whether the length of time thesatellite (or payload on board the satellite) has remained inconsecutive “High Idle” periods is larger than an idle time thresholdvalue T_(idle) and whether T_(current.time)−T_(on)>T_(wait) may bedetermined. If operation 914 returns “NO,” the sub-process 900 may endat block 922. It should be noted that the sequence of blocks 910 and 914is irrelevant and, in some implementations, they may be in a differentorder or even combined (e.g., both blocks combined into one conditionaloperation). If either of the operations 910 or 914 returns “YES,” thesub-process 900 may proceed to block 916, at which the satellite (orpayload on board the satellite) currently being processed may be putinto the “Low Idle” mode. At block 916, “Low Idle” may be assigned asthe current operational mode, “High Idle” may be assigned as theprevious operational mode, previously scheduled upcoming “High Idle”periods may be changed to “Low Idle” periods, and the total scheduledenergy consumption Q_(total) may be adjusted to account for the changeto “Low Idle” as well. With the previously scheduled N_(high.idle) “HighIdle” periods changed to be “Low Idle” periods, the N_(high.idle)entries in the array C may be changed to P_(idle) at block 916 as well.In at least one implementation, the adjustment to Q_(total) may beperformed as Q_(total)=Q_(total)−N_(high.idle) (P_(high.idle)−P_(idle))Δt_(s). It should be noted that, in some implementations, the satellitecoverage provisioning process described herein may be performedbeforehand. That is, this process may not be executed in real time suchthat every decision may not be carried out immediately, but instead thisprocess may be pre-performed such as to prepare a schedule for thefuture. Thus, previously scheduled “High Idle” periods may be adjustedto be “Low Idle” periods and this adjustment may not affect thesatellite's current operation. Additionally or alternatively, in someimplementations, the satellite coverage provisioning process may berepeatedly iteratively such that periods previously scheduled for thesatellite (or payload on board the satellite) may be changed duringsuccessive iterations.

From block 916, the sub-process 900 may proceed to block 918, at whichwhether the satellite (or payload on board the satellite) currentlybeing processed is in an eclipse period is determined. If operation 918determines that the ECLIPSE is true, at block 920, the power consumptionfor eclipse Q_(eclipse) may be adjusted for all previously scheduled“High Idle” eclipse intervals to account for the change to “Low Idle.”In one implementation, such an adjustment may be performed by repeatingthe calculation Q_(eclipse)=Q_(eclipse)−(P_(high.idle)−P_(idle)) Δt_(s)for all consecutive pervious states in ECLIPSE and “High Idle” mode. Ifoperation 918 returns “NO,” or alternatively, the block 920 finishes,the sub-process 900 may end at block 922.

FIG. 10 illustrates an exemplary system configuration suitable topractice aspects of the present disclosure. As illustrated in thefigure, an exemplary computing apparatus 1000 may include a processor1020, memory 1030, support/auxiliary equipment 1010 and networkinterface 1040 communicatively coupled one to another throughinterconnect equipment 1050. Interconnect equipment 1050 includesinterface, control and processing circuitry sufficient to facilitateinformation exchange between components of computing apparatus 1000. Itis to be understood that while interconnect equipment 1050 isillustrated in FIG. 10 as a single bus, interconnect equipment 1050 mayinclude multiple, different signal-bearing media and may implementmultiple, different interconnect hardware configurations, media access,signaling, pathfinding and/or routing techniques, communicationprotocols, etc. Computing apparatus 1000 may represent an implementationof computing apparatus 204 of FIG. 2.

Processor 1020 may be constructed or otherwise configured to, amongother things, execute processing instructions that implement variousfunctional modules and all processes as described herein, such as thosedescribed herein with reference to FIGS. 2 and 4-9. It is to beunderstood that the present disclosure is not limited to a particularhardware configuration or instruction set architecture of processor1020, which may be configured by numerous structures that performequivalently to those illustrated and described herein. Moreover, it isto be understood that while the processor 1020 is illustrated as asingle component, certain implementations may include distributedprocessing implementations through multiple processing elements.Processor 1050 may be realized through a wide variety of processing andinterface circuitry including, but not limited to analog-to-digitalconverter circuits, digital-to-analog converter circuits, fixed digitallogic circuits, programmable digital logic circuits, applicationspecific circuits, etc., to implement, among other components, generaldata processors, data-specific processors, signal converters andconditioners, analog and digital signal processors, and so on. Thosehaving skill in the art will recognize numerous processingconfigurations by which the present disclosure can be embodied withoutdeparting from the spirit and intended scope thereof.

Memory 1030 may be utilized to store data and processing instructions onbehalf of the exemplary computing apparatus 1000. Memory 1030 mayinclude memory that is distributed across components, to include, amongothers, cache memory and pipeline memory. Memory 1030 may includepersistent memory, such as one or more hard disk drives, or may beimplemented in multiple persistent memory devices, which may beinterconnected by a communication network, such as to implement one ormore databases. Memory 1030 may include electrical, magnetic and/oroptical storage media and associated access mechanisms including, butnot limited to electronic random access and/or read-only memory, flashmemory, hard disk drive memory, compact disk memory and digitalversatile disk memory to implement, among other things, executable codestorage, application data storage, instruction and data registers, andinstruction and data caches.

Network interface 1040 may include network cards and modules forcommunication with satellites (or payloads on board the satellites)and/or data storage devices, such as, for example, the satelliteinformation repository 202 of FIG. 2 (e.g., if the satellite informationrepository 202 is not co-located with the apparatus 1000). In certainimplementations, such characterization is modeled for purposes ofcontrolling the constellation of satellites for service coverageprovisioning, as discussed in detail herein. Communication operationsimplemented by network interface 1040 may include networkcommunications, e.g., Ethernet, Wi-Fi, cellular, etc., and serialcommunications, e.g., Universal Serial Bus (USB), RS-232, etc.Implementations are not limited to any particular communication media,signal type or protocol; those having skill in the art will recognizenumerous communication techniques that can be used without departingfrom the spirit and intended scope of the concepts disclosed herein.

Support/auxiliary equipment 1010 may include input/output circuitsincluding a display, a keyboard, a mouse, a track ball, a stylus, atouch screen, a touchpad, and/or other devices suitable to provide inputto the computing apparatus 1000.

Certain aspects of the present general concepts disclosed herein providefor functional components to manufactured, transported, marketed and/orsold as processor instructions encoded on computer-readable media.Implementations, when so embodied, can be practiced regardless of theprocessing platform on which the processor instructions are executed andregardless of the manner by which the processor instructions are encodedon the computer-readable medium.

It is to be understood that the computer-readable medium described abovemay be any non-transitory medium on which the instructions may beencoded and then subsequently retrieved, decoded and executed by aprocessor, including electrical, magnetic and optical storage devices.Examples of non-transitory computer-readable recording media include,but are not limited to, read-only memory (ROM), random-access memory(RAM), and other electrical storage; CD-ROM, DVD, and other opticalstorage; and magnetic tape, floppy disks, hard disks and other magneticstorage. The processor instructions may be derived from algorithmicconstructions in various programming languages that realize the presentgeneral inventive concepts, for example, as exemplified by theimplementations described above.

The descriptions above are intended to illustrate possibleimplementations of the present concepts and are not restrictive. Manyvariations, modifications and alternatives will become apparent to theskilled artisan upon review of this disclosure. For example, componentsequivalent to those shown and described may be substituted therefore,elements and methods individually described may be combined, andelements described as discrete may be distributed across manycomponents. Furthermore, though certain constraints and determinationsare described herein as being based on power consumption, suchconstraints and determinations could equally well be based on electricalenergy consumption such that the terms power consumption and electricalenergy consumption may be understood to encompass one another herein.The scope of the disclosure should therefore be determined not withreference to the description above, but with reference to the appendedclaims, along with their full range of equivalents.

What is claimed is:
 1. A method of provisioning satellite coverage for aservice area, the method comprising: updating power consumption statesfor satellites in a constellation of satellites; determining whethereach satellite of the constellation of satellites is required to be in aminimal power consumption mode based on its updated power consumptionstate; scheduling each satellite required to be in the minimal powerconsumption mode to enter the minimal power consumption mode; forsatellites that are not required to be in the minimal power consumptionmode, calculating a power consumption score representing a powerconsumption level relative to a limit; sorting the satellites that arenot required to be in the minimal power consumption mode according totheir power consumption scores; determining, based on the sorted order,whether at least some of the satellites that are not required to be inthe minimal power consumption mode can be put into a reduced powerconsumption mode based on the satellite's power consumption score andcoverage of the service area; scheduling each satellite that can be putinto the reduced power consumption mode to enter the reduced powerconsumption mode; determining whether each of the satellites that are inthe reduced power consumption mode can be put into the minimal powerconsumption mode; and scheduling each satellite that is in the reducedpower consumption mode that can be put into the minimal powerconsumption mode to enter the minimal power consumption mode.
 2. Themethod of claim 1, wherein sorting the satellites comprises sorting thesatellites according to the power consumption score in a descendingorder.
 3. The method of claim 1, wherein calculating the powerconsumption score comprises: calculating the power consumption score asa ratio of power consumption Q_(total) in sliding window of time to amaximal cumulative power consumption threshold Q_(off):S=Q_(total)/Q_(off).
 4. The method of claim 3, further comprising, whena satellite is in an eclipse period, adjusting its power consumptionscore by a ratio of a power deficiency variable Q_(deficiency) to anemergency threshold for eclipse power consumption Q_(max.eclipse) whenQ_(deficiency) is larger than zero.
 5. The method of claim 4, whereinthe adjustment is performed by a factor multiplied to the ratio ofQ_(deficiency)/Q_(max.eclipse).
 6. The method of claim 1, furthercomprising: determining a time to reboot a satellite when the satelliteis in the minimal power consumption mode.
 7. The method of claim 1,further comprising: determining a satellite needs to be put into theminimal power consumption mode when the satellite's total cumulativepower consumption will exceed a threshold at any time during a slidingwindow.
 8. A computing apparatus comprising: one or more networkinterfaces for connection to a constellation of satellites; a memory;and a processor coupled to the one or more network interfaces and thememory, and configured to: update power consumption states forsatellites in a constellation of satellites; determine whether eachsatellite of the constellation of satellites is required to be in aminimal power consumption mode based on its updated power consumptionstate; schedule each satellite required to be in the minimal powerconsumption mode to enter the minimal power consumption mode; forsatellites that are not required to be in the minimal power consumptionmode, calculate a power consumption score representing a powerconsumption level relative to a limit; sort the satellites that are notrequired to be in the minimal power consumption mode according to theirpower consumption scores; determine, based on the sorted order, whetherat least some of the satellites that are not required to be in theminimal power consumption mode can be put into a reduced powerconsumption mode based on the satellite's power consumption score andcoverage of the service area; schedule each satellite that can be putinto the reduced power consumption mode to enter the reduced powerconsumption mode; determine whether each of the satellites that are inthe reduced power consumption mode can be put into the minimal powerconsumption mode; and schedule each satellite that is in the reducedpower consumption mode that can be put into the minimal powerconsumption mode to enter the minimal power consumption mode.
 9. Theapparatus of claim 8, wherein to sort the satellites that are not in theminimal power consumption mode the processor is further configured tosort the satellites according to the power consumption score in adescending order.
 10. The apparatus of claim 8, wherein to calculate thepower consumption score the processor is further configured to:calculate the power consumption score as a ratio of cumulative powerconsumption in a sliding window of time to a maximal power consumptionthreshold Q_(off): S=Q_(total)/Q_(off).
 11. The apparatus of claim 10,wherein the processor is further configured to, when a satellite is inan eclipse period, adjust its power consumption score by a ratio of apower deficiency variable Q_(deficiency) to an emergency threshold foreclipse power consumption Q_(max.eclipse) when Q_(deficiency) is largerthan zero, wherein the adjustment is performed by a factor multiplied tothe ratio of Q_(deficiency)/Q_(max.eclipse).
 12. The apparatus of claim8, wherein the processor is further configured to: determine a time toreboot a satellite when the satellite is in the minimal powerconsumption mode.
 13. The apparatus of claim 8, wherein the processor isfurther configured to: determine a satellite needs to be put into theminimal power consumption mode when the satellite's total cumulativepower consumption will exceed a threshold at any time during a slidingwindow.
 14. One or more non-transitory computer readable storage mediahaving instructions encoded thereon that, when executed by a processor,cause the processor to: update power consumption states for satellitesin a constellation of satellites; determine whether each satellite ofthe constellation of satellites is required to be in a minimal powerconsumption mode based on its updated power consumption state; scheduleeach satellite required to be in the minimal power consumption mode toenter the minimal power consumption mode; for satellites that are notrequired to be in the minimal power consumption mode, calculate a powerconsumption score representing a power consumption level relative to alimit; sort the satellites that are not required to be in the minimalpower consumption mode according to their power consumption scores;determine, based on the sorted order, whether at least some of thesatellites that are not required to be in the minimal power consumptionmode can be put into a reduced power consumption mode based on thesatellite's power consumption score and coverage of the service area;schedule each satellite that can be put into the reduced powerconsumption mode to enter the reduced power consumption mode; determinewhether each of the satellites that are in the reduced power consumptionmode can be put into the minimal power consumption mode; and scheduleeach satellite that is in the reduced power consumption mode that can beput into the minimal power consumption mode to enter the minimal powerconsumption mode.
 15. The non-transitory computer readable storage mediaof claim 14 having additional instructions encoded thereon that, whenexecuted by the processor, cause the processor to: sort the satellitesthat are not in the minimal power consumption mode by sorting thesatellites according to the power consumption score in a descendingorder.
 16. The non-transitory computer readable storage media of claim14 having additional instructions encoded thereon that, when executed bythe processor, cause the processor to calculate the power consumptionscore by calculating the power consumption score as a ratio ofcumulative power consumption in a sliding window of time to a maximalpower consumption threshold Q_(off): S=Q_(total)/Q_(off).
 17. Thenon-transitory computer readable storage media of claim 16 havingadditional instructions encoded thereon that, when executed by theprocessor, cause the processor to, when a satellite is in an eclipseperiod, adjust its power consumption score by a ratio of a powerdeficiency variable Q_(deficiency) to an emergency threshold for eclipsepower consumption Q_(max.eclipse) when Q_(deficiency) is larger thanzero.
 18. The non-transitory computer readable storage media of claim17, wherein the adjustment is performed by a factor multiplied to theratio of Q_(deficiency)/Q_(max.eclipse).
 19. The non-transitory computerreadable storage media of claim 14, having additional instructionsencoded thereon that, when executed by the processor, cause theprocessor to: determine a time to reboot a satellite when the satelliteis in the minimal power consumption mode.
 20. The non-transitorycomputer readable storage media of claim 14, having additionalinstructions encoded thereon that, when executed by the processor, causethe processor to: determine a satellite needs to be put into the minimalpower consumption mode when the satellite's total cumulative powerconsumption will exceed a threshold at any time during a sliding window.